int i=0;
void setup() {

 pinMode(4, OUTPUT);
 pinMode(3, OUTPUT);
 pinMode(2, OUTPUT);
 pinMode(5, OUTPUT);
 pinMode(11, INPUT);
 pinMode(12, INPUT);

}

void loop() {
    if (digitalRead(11)==1){
         i=i+1;
    }
    if (digitalRead(12)==1){
        if (i>0)
             i--;
    }
  switch(i){
      case 0:
             
             digitalWrite(4, LOW);
             digitalWrite(3, LOW);
             digitalWrite(2, LOW);
             digitalWrite(5, LOW);
             break;
    case 1:
             
             digitalWrite(4, HIGH);
             digitalWrite(3, LOW);
             digitalWrite(2, LOW);
             digitalWrite(5, LOW);   
             break;
   case 2:
             digitalWrite(4, HIGH);
             digitalWrite(3, HIGH);
             digitalWrite(2, LOW);
             digitalWrite(5, LOW);       
             break;
  case 3:
             digitalWrite(4, HIGH);
             digitalWrite(3, HIGH);
             digitalWrite(2, HIGH);
             digitalWrite(5, LOW);
             break;
 case 4:
             digitalWrite(4, HIGH);
             digitalWrite(3, HIGH);
             digitalWrite(2, HIGH);
             digitalWrite(5, HIGH);
             break;
      default:
             i=1;
             break;


  }
  delay(100);
}